Scraper-blade type belt cleaners as applied to light-duty belt conveyance systems are usually composed of little more than a piece of plastic sheet stock, typically polyethylene, that has been machined to have an angled edge. The machined edge serves as a belt scraper when held in proximity to or against the belt, typically by simple bolted angles, channels or other brackets, often in “one-of-a-kind” mounting arrangements. These belt cleaners are often located on a conveyor system near the location at which material is discharged from the conveyor belt (i.e., near the head or snub pulley). Since these belt cleaners rarely incorporate any type of blade tensioning system, regular adjustment of the mounting arrangement is required to maintain blade pressure against the belt for proper operation. Due to the difficulty in removing and re-installing the blade assembly when these mounting arrangements are used, sanitary cleaning operations are limited as a practical matter to In-Place Cleaning (IPC) techniques.
These “one-of-a-kind” belt cleaners are often designed specifically for particular existing equipment and are retrofit into such existing equipment by plant maintenance personnel, however, some Original Equipment Manufacturers (OEMs) do provide inexpensive cleaners with their conveyance systems that are likewise impractical for easy use. Moreover, OEM process equipment manufacturers will sometimes use a device similar to a belt cleaner to remove product from process rollers or to aid in directing the product carried by the conveyor (e.g., guide rails or flow directors) or in shaping the product (e.g., dough rounders)
Certain “few-of-a-kind” scraper blade type belt cleaners found on OEM designed conveyance systems and related process equipment incorporate a simple compression spring assembly or similar mechanism to permit tensioning of the scraper blade against the conveyor belt. These units are typically difficult, if not impossible, to properly clean and sanitize, and normal adjustment of the spring tension often requires special tools and skilled personnel. Further, small hardware or other parts often used on such systems are loosed or disassembled for cleaning and can easily find their way into the process stream. Due to the relative complexity of a spring assembly, such tensioned systems are seldom designed and retrofit to existing equipment by plant maintenance personnel.
One commercially available belt scraper that is purportedly configured specifically for food grade applications is the Piglet™ scraper, which is offered for both primary (“Pre-Cleaner”) and secondary (“Post-Cleaner”) scraper configurations. Elements of the this scraper that are both undesirable and unlike the present invention include:                an internal elastomeric tensioner and end-housing which, due to the inherent difficulty of disassembling and cleaning such an assembly and to the lack of adequate seals, presents a potentially serious microbiological hazard when used in food grade applications;        a tensioner system which is difficult to utilize in the field due to the need for hand-tool adjustment of the tension and the limited life of the set-screw type fasteners used to adjust the tension after each cleaning;        a removal and installation scheme that requires the scraper blade to be “slid” off the ends of the blade-holder, thus making regular disassembly and cleaning extremely difficult; and        a segmented blade in which contaminating materials and moisture can easily become entrapped in spaces between the blade and blade holder, and between adjacent ones of the four-inch blade segments.        
Further, another company offers a Saber® Belt Cleaner, which is not designed for sanitary/food grade applications, but is “upgraded” by offering a scraper blade fabricated from food-grade material. This system utilizes an incremental tensioning system, called the “Twister Tensioner”, and utilizes a polyurethane torsion element. The tensioning unit is not a sanitary design and presents a potentially serious microbiological hazard because static material and moisture can accumulate between the Twister Tensioner and the blade holder tube. In addition, cleaning and/or inspecting this belt cleaner requires complete disassembly which creates a difficulty while exposing the processing line to loose hardware that can easily find its way into the product as foreign matter.
Finally, ASGCO Manufacturing offers a modified version of the Mini-Skalper™ scraper which is “upgraded” for sanitary/food-grade applications by offering both a food-grade scraper blade and by changing the blade holder and components of the Roto-Twist™ tensioner to stainless steel materials and construction.
Accordingly, there is a need for a belt scraping apparatus that is suitable for use in food-grade and/or other sanitary cleaning operations, although its use is not limited thereto. In addition, it would also be desirable that both the arrangement and materials thereof be suitable for use in a sanitary operation, including the arrangement and materials of the scraper blade, the blade holder, the blade tensioning mechanism and the system arrangement.
To this end, a tensioner includes an outer collar affixed to a housing, an inner collar affixed to a blade holder, and a torsion spring coupled between the inner and outer collars for urging a blade toward a belt.
In the Drawing, where an element or feature is shown in more than one drawing figure, the same alphanumeric designation may be used to designate such element or feature in each figure, and where a closely related or modified element is shown in a figure, the same alphanumerical designation primed may be used to designate the modified element or feature. Similarly, similar elements or features may be designated by like alphanumeric designations in different figures of the Drawing and with similar nomenclature in the specification, but in the Drawing are preceded by digits unique to the embodiment described. For example, a particular element may be designated as “xx” in one figure, by “1xx” in another figure, by “2xx” in another figure, and so on. It is noted that, according to common practice, the various features of the drawing are not to scale, and the dimensions of the various features are arbitrarily expanded or reduced for clarity.